The vast ice sheet covering Greenland could melt more quickly in the future than existing models predict, new research suggests.

Scientists looked at satellite data collected by NASA’s ICESat spacecraft and Operation IceBridge and plotted the elevation of 100,000 sites on Greenland from 1993 to 2012.

The researchers were able to create new, more precise estimates for how much ice had melted in the past. They also found that the ice melts in a rather complex pattern, which should be of interest to scientists trying to predict how much ice will disappear in the future. [Images: Greenland’s Gorgeous Glaciers]

More than a mile thick in most areas, the Greenland Ice Sheet covers nearly all of interior Greenland, an Arctic island about three times the size of Texas. If the entire ice sheet melted, sea levels around the world would rise about 20 feet (6 meters), according to the National Snow and Ice Data Center.

Though such a catastrophic scenario isn’t likely to happen anytime soon, smaller increases in sea level could still boost the power of coastal storms, threaten to flood major cities and displace millions of people. During the 20th century, sea levels rose by about 6.7 inches (17 centimeters). According to the latest report from the Intergovernmental Panel on Climate Change (IPCC), the current scientific consensus is that sea levels could creep up by 11 inches to 38 inches (28 to 98 cm) by 2100, in part because of melting in the Greenland and Antarctic ice sheets.

The new research found that an average of 243 gigatons (or 66.5 cubic miles) of the Greenland Ice Sheet melted each year from 2003 to 2009. (The scientists had the most comprehensive data for this period.) That’s enough meltwater to raise oceans by about 0.027 inches (0.68 millimeters) per year, the researchers said.

The study didn’t make any exact predictions for how much of Greenland’s ice may melt in the future, but the authors think that current models underestimate the extent of the problem.

“My personal opinion is that most of the predictions of this as far as Greenland is concerned are too low,” study author Beata Csatho, an associate professor of geology at the University at Buffalo, said in a video statement.

Existing models for predicting changes in ice-sheet melt and sea-level rise are typically extrapolated from data on just four of Greenland’s 242 glaciers: Jakobshavn, Helheim, Kangerlussuaq and Petermann. That’s a problem, according to the study’s authors, because glaciers — even ones right next to each other — can behave quite differently in any given year. Today’s models also tend to ignore southeast Greenland’s ice cover, which is experiencing heavy losses, the researchers found. In 2005, melting in this region accounted for more than half of the losses to the Greenland Ice Sheet.

Csatho and her colleagues say it’s not easy to predict how glaciers will respond to global warming, because they don’t always melt as the temperature rises. Their data showed that sometimes the glaciers covering Greenland thickened when the temperature rose, while some areas both thinned and thickened, with abrupt reversals.

To help other researchers create better prediction models, the scientists put all of Greenland’s glaciers into seven groups, based on the characteristics of their melting behavior from 2003 to 2009.

“Understanding the groupings will help us pick out examples of glaciers that are representative of the whole,” Csatho said in a statement. “We can then use data from these representative glaciers in models to provide a more complete picture of what is happening.”

GALVESTON, Texas (Reuters) – When Hurricane Ike hit this city on the Gulf of Mexico, William Merrell found himself trapped in a second-floor apartment as storm waters coursed eight feet deep through the floor below. “I had time to think,” said the professor and chair of marine sciences at Texas A&M University Galveston.

One thing he thought about was the Dutch Delta Works, a vast coastal protection system he had seen several years earlier on a trip to the Netherlands.

That led to his big idea: build a 60-mile-long, 17-foot-tall dike that would guard against the next hurricane that hits the long, thin barrier island on which Galveston sits. Like its Dutch inspiration, his idea included massive gates that would swing shut as a storm approached, blocking the 1.7-mile-wide entrance to Galveston Bay. The gate would protect low-lying parts of metro Houston, home to hundreds of thousands of people and an oil and petrochemicals complex essential to the U.S. economy.

Ike hammered Galveston and its 57,000 inhabitants, funneling a surge of water around an existing seawall and into the bay. Eighty percent of Galveston’s homes were damaged or destroyed, including Merrell’s apartment building. The hurricane killed 112 people in the U.S., including 36 in the Houston-Galveston area alone, and caused nearly $30 billion in damage.

The toll left little doubt that something was needed to defend residents and the U.S. economy against the next big storm. “It’s a national security issue,” said Bob Mitchell, president of the nonprofit Bay Area Houston Economic Partnership.

Six years on, Galveston and Houston, the nation’s fourth largest city, are as vulnerable as when Ike hit. No major projects are under way to fend off surging seas.

Pilings for a new house rise many feet in the air at a construction site on west Galveston Island, T …

Instead, Merrell’s “Ike dike” remains the leading proposal for coastal defense. Nineteen cities and towns lining Galveston Bay back it, but with an estimated cost of $6 billion, the Ike dike is far from a done deal. It has no big money behind it.

For the Ike Dike to evolve beyond wishful thinking, Texas would have to get funding from Congress and support from the U.S. Army Corps of Engineers, the go-to federal agency for coastal protection.

But the corps has been sidelined by new spending limits, and Texas’s advocates in Congress have been silent. Major local powers – the city of Houston and the oil and petrochemicals industries – have yet to weigh in on Merrell’s plan or a competing idea pushed by Rice University.

“It’s absurd it’s been so slow,” Merrell said.

POLICY VACUUM

The paralysis in Texas reflects a troubling truth: The United States lacks a unified national response to the threat posed by rising sea levels. The policy vacuum leaves vulnerable communities to come up with their own self-defense plans and then hope to snag federal dollars before the next big storm.

“Without some sort of national perspective on this, it pits parts of the country against each other … And Houston is stuck right in the middle of it,” said Richard Luettich Jr, a marine scientist at the University of North Carolina in Chapel Hill and chairman of a National Research Council panel on coastal risk. The panel in July said U.S. government agencies have “no central leadership or unified vision” on reducing coastal risk – a failure that extends even to towns that are literally washing into the sea.

As previous articles in this series showed, the threat of rising seas is not an alarmist prediction. It is already a reality, resulting in increased tidal flooding and worsening storm damage along much of the U.S. coast. And even as the water has risen, subsidies for flood insurance, utilities and disaster bailouts are encouraging development along some the nation’s most at-risk shores.

For places like the Texas Gulf coast, which on average gets slammed with a major hurricane every 15 years, higher waters mean a storm today will tend to be much more dangerous than one of equivalent strength several decades ago.

“Sea level is not going to kill you today,” said Larry Atkinson, a professor at the Center for Coastal Physical Oceanography at Old Dominion University in Norfolk, Virginia. “It’s the storm surge that comes on top of the sea level rise.”

The probability of a flood in New York like the one that accompanied Hurricane Sandy in 2012, while still low, has increased about 50 percent since 1950, and tripled for parts of the New Jersey shoreline, researchers from the National Oceanic and Atmospheric Administration said in a September 2013 report.

At least $1.4 trillion worth of property – homes and businesses – sits within about one-eighth of a mile of the U.S. coastline. That number comes from a Reuters analysis of data provided by RealtyTrac. Incomplete data for some areas means the actual total is probably much higher.

More than 40 counties have coastal property worth $10 billion or more, the analysis found. In Miami-Dade County alone, about $94 billion worth of property lies along tidal waters.

Despite so much at stake, Washington shies away from large-scale action to defend the coast. Instead, it focuses on holding the line with smaller, temporary measures – dumping sand on eroded beaches, or building seawalls, breakwaters and berms to protect scattered sections of populated shoreline.

The price of these piecemeal measures is high: New seawalls average $36 million per mile, and a new levee is $10 million per mile, according to a 2010 study by Old Dominion. That doesn’t include maintenance.

But failure to act carries a high cost, too. In Galveston County, nearly 70 percent of businesses and 75 percent of jobs are in hurricane flood zones, according to a Reuters analysis of data compiled by the U.S. Bureau of Labor Statistics. The picture is similar in other parts of the country: In Norfolk, 76 percent of jobs are in hurricane flood zones. In Charleston, South Carolina, it’s a little more than half.

The federal government has typically waited to take major preventive action until after a disaster, when public awareness provides political impetus.

Damaged neighborhoods surrounded by water are seen from a U.S. Air Force helicopter conducting searc …

After Hurricane Katrina in 2005, emergency congressional action gave Louisiana $14.5 billion to build a comprehensive system of levees, dikes and floodwalls to safeguard the New Orleans area. This year, the levee system was accredited as safe enough to allow residents to get cheaper flood insurance.

Similar moves after Hurricane Sandy in 2012 provided much of the $20 billion New York City needs over the next decade to build 250 projects to protect against storm surges.

Many other cities with tens of billions of dollars in assets at risk have no recent storm to point to. They remain vulnerable. Norfolk’s mayor says his city needs a billion dollars for flood gates, raised roads and storm water improvements to protect its shoreline.

THAT OTHER DISASTER

Ike was the third most destructive storm in U.S. history after Katrina and Sandy. It would seem to have justified action on behalf of metro Houston.

But two days after Ike hit, investment bank Lehman Brothers filed for bankruptcy, triggering a global financial crisis that quickly overshadowed Texas’s natural disaster. The state didn’t ask for any money for prevention, just for relief to clean up the mess. Galveston was represented in Congress at the time by libertarian Republican Ron Paul, who voted against any Federal Emergency Management Agency disaster aid anywhere. Paul declined to comment.

The large seawall that protects Galveston from major storms and the rising waters of the Gulf of Mex …

“All the coverage Katrina got and Sandy got, Ike just didn’t get,” Merrell said. Now, years later, “it’s hard to get someone’s attention when there’s not a hurricane.”

Most of the post-Ike disaster relief FEMA gave Texas has been spent to rebuild in the same places, as required by federal law. The agency is also offering subsidized flood insurance, another incentive to rebuild in harm’s way. Last year, Houston and Galveston officials and homeowners joined a nationwide rally to prod Congress to maintain below-market rates on flood insurance.

Galveston, like many cities along the nation’s imperiled shores, continues to encourage development. Over the past two years, the Galveston planning commission approved 81 of 85 applications to build even closer to the beach than normally permitted by state law, records show. New development is rising along the disappearing shore. Many of the expensive homes are perched on stilts.

Galveston and hurricanes have long shared a singular notoriety. On Sept. 8, 1900, an unnamed hurricane nearly wiped the city off the map, killing more than 6,000 people. To this day, it remains the deadliest natural disaster in U.S. history.

Within a couple of years, construction was under way on a seawall to protect the city at the northeastern end of the island. It now stands 17 feet high. Originally about three miles long, it was extended over the ensuing decades to its current 10-mile length.

But Galveston Island is nearly three times longer than that. Most of its Gulf-facing shore remains exposed. Ike’s storm surge didn’t top the existing seawall, but it did go around it. A 20-foot-high surge shot into the bay, wreaking havoc.

The foundation of a structure swamped in seawater is seen in the former Brownwood neighborhood, whic …

Even without storms, rising seas are chewing away at the island’s unprotected beaches at a rate of two to 11 feet a year. The tide gauge at the city’s Pier 21 has shown a rise in relative sea level of 25 inches since 1908 – the largest increase over the past century at any of the scores of gauges monitored by NOAA.

About one-third of that rise was from oceans rising globally as water warms and polar ice melts. The remaining two-thirds resulted from land sinking due to subsidence, which happens when the removal of underground water, oil and gas causes the land to pancake.

Galveston Island is far from the only thing at stake. Between it and the mainland is Galveston Bay, connected to Houston by the 50-mile Houston Ship Channel, home to one of the world’s busiest ports. The entire area, once marshy wetlands, is lined with suburbs and at least $100 billion in oil refineries, chemical plants and related infrastructure. Metro Houston accounts for about 26 percent of U.S. gasoline production, 42 percent of base chemicals production, and 60 percent of jet fuel output.

A 25-foot storm surge pushing into the bay and up the ship channel would cause “economic catastrophe” to the nation and poison the bay in “the worst environmental disaster in United States history,” according to Rice University’s Severe Storm Prediction, Education, and Evacuation from Disasters Center. The Ike surge was just shy of that scenario.

“We do think we have a strong case for [protecting] a national strategic asset,” said Robert Eckels, a Houston lawyer, businessman and former chief executive of the Harris County government. Eckels was appointed a month after Ike to chair the Governor’s Commission for Disaster Recovery and Renewal.

The road dead ends into water at the San Jacinto battlefield in Houston, Texas March 6, 2014. REUTER …

The commission first heard Merrell’s pitch four months after Ike. Members liked what they heard and recommended a feasibility study. In early 2010, the commission created a six-county “recovery district,” a non-profit also headed by Eckels, to look at ways to protect metro Houston. It promptly ran out of money: The $4 million for the study got tangled in a legal dispute over funding for rebuilding public housing in Galveston.

For the next three years, the recovery district was dormant.

Meanwhile, Rice University’s Sspeed Center in Houston had come up with a rival plan – and it didn’t include a wall along the gulf.

Instead, the Rice team proposed building what it called the Centennial Gate farther inland, at the entrance to the Houston Ship Channel. The gate’s two metal walls would swing shut to block any storm surge threatening the area. The cost, about $1.5 billion, could be at least partly covered by bond issues backed by taxpayers or industry, the Rice team said.

Merrell rejected the Rice plan as “a waste of money.” Any effective protection for the entire area would, like the Dutch Delta Works, have to armor the outermost shore, not the inner bay, he said.

Jim Blackburn, a professor of environmental law at Rice’s engineering school, helped develop the Sspeed Center’s plan. He criticized the Ike dike for protecting shoreline that should be left in its natural state. “Perhaps the coast should just be a place to visit,” Blackburn told reporters in 2009.

William Merrell, Chairman of the Marine Sciences Department at Texas A&M University, works on the &q …

Galveston Bay has lost a third of its wetlands to development since the 1950s, removing a natural buffer against flooding and storm surge. The Rice plan would set aside about 225,000 acres of low-lying land and undeveloped coast around the bay to reduce storm risk. This proposed national recreation area would also draw in birdwatchers, kayakers and other tourists. “A no-brainer,” Blackburn said.

But communities around Galveston Bay hit hard at the Rice plan for leaving them unprotected outside the Centennial Gate.

“Collateral damage,” is how a LaPorte City Council resolution described their city’s fate under the plan. A blogger complained: “They have already drawn us off the damn maps.”

Past attempts to protect vulnerable shores have run into the same problem.

The new levees around New Orleans don’t protect towns just to the north, south and west. Residents of LaPlace, a town of 32,000 people northwest of New Orleans, blamed the improved levees protecting their neighbors for their own unprecedented flooding by Hurricane Isaac in 2012.

A centerpiece of New York’s plan – 10 miles of berms and floodwalls forming a “Big U” around lower Manhattan – would safeguard Wall Street. But some people complain it would push more water onto New Jersey, Brooklyn and Queens shores.

Merrell’s Ike dike plan elicited similar complaints. Initially, he suggested that the dike simply trace a path from the end of the existing seawall along a highway that weaves beside the shoreline to the southwestern tip of the island. The highway would be raised atop the new wall.

But the strip of land that would lie between highway and beach contains $810 million in real estate, 11.2 percent of the island’s total, according to the county appraisal office. And if it were left outside the Ike dike, it could be washed away.

“If it’s on the highway side, it’s going to leave us underwater,” said Tom Booth, a retiree who lives with his wife in a condominium between the highway and the breezy shore where pelicans patrol the sky.

PLUGGING AWAY

As a solution, Merrell would build the wall right along the beach and cover it with sand and salt-resistant plants to emulate a dune line. That revision still raised issues of cost, lost views and restricted beach access, among other things.

Merrell continued to refine and tout the Ike dike plan. He talked frequently with engineers he met through connections at Delft University of Technology, which helped design the Dutch Delta Works. In September 2012, he helped lead a group of two dozen Texas business people, academics and engineers on a tour of the Netherlands’ flood and erosion projects. Many of these were started after the North Sea flood of 1953 killed nearly 2,000 people.

For now, his Ike dike idea and the competing Rice concept are staying alive on local grants – $4 million here, $3 million there. Area politicians have been pressing the two camps to unite. And recently, the Rice team modified its plan so that it resembles something very close to the Ike dike: In addition to the gate on the Houston Ship Channel, it now has sea gates and raised highways along the Gulf shore, eliminating the major objection that it left too many communities exposed.

But with no agreed-upon proposal to evaluate, the all-important Army Corps of Engineers has remained out of the picture. Sharon Tirpak, the corps’ project manager for a Texas coastal flooding study, stopped looking at Galveston Bay earlier this year after Congress imposed a three-year, $3 million limit on feasibility studies. Those caps are too strict to allow for the large studies required for the type of big fix metro Houston needs.

Only a congressional waiver can get around those limits, and as Tirpak told the Galveston City Council in April: “The political support, you don’t have it in Texas.”

She had a point.

Governor Rick Perry hasn’t commented publicly on the Ike Dike or any other storm protection plan. The state’s two U.S. senators, Republicans Ted Cruz and John Cornyn, are noncommittal, as is the U.S. congressman who replaced Ron Paul.

The oil and petrochemical industries, whose multibillion-dollar facilities would be protected by both competing plans, is in a delicate position: Texas leads the nation in emitting greenhouse gases, which are at the heart of the debate over human-induced climate change and thus rising sea levels. The industry’s powerful lobby said it is still evaluating the rival proposals.

SAXIS, Virginia (Reuters) – Chincoteague is the gateway to a national wildlife refuge blessed with a stunning mile-long beach – a major tourist draw and source of big business for the community.

But the beach has been disappearing at an average rate of 10 to 22 feet a year, as a warming planet and other forces lift sea levels. The access road and parking lot have been rebuilt five times in the past decade because of coastal flooding, at a total cost of $3 million.

Officials who run Chincoteague National Wildlife Refuge say they face a losing battle against rising sea levels. In 2010, they proposed to move the beach to a safer spot, shrink the parking lot, and shuttle in tourists by bus.

The town revolted. Chincoteague wants the federal government to continue to rebuild rather than retreat. Four years on, after a series of angry public meetings, the sea keeps eating the shore, and the government keeps spending to fix the damage.

The people of Chincoteague are engaged in a battle at the water’s edge against rising seas. All along U.S. shores, people, businesses and governments are confronting rising seas not as a future possibility. For them, the ocean’s rise is a troubling everyday reality.

Saxis Island resident and duck decoy carver Grayson Chesser takes to the water off this historic fis …

Reuters gathered more than 25 million hourly readings from National Oceanic and Atmospheric Administration tide gauges at nearly 70 sites on the U.S. coast and compared them to flood thresholds documented by the National Weather Service.

The analysis was then narrowed to include only the 25 gauges with data spanning at least five decades. During that period, the average number of days a year that tidal waters reached or exceeded NOAA flood thresholds increased at all but two sites and tripled at more than half of the locations.

The coastal flooding is often minor. Its cumulative consequences are not. As flooding increases in both height and frequency, it exacts a toll in closed businesses, repeated repairs, and investment in protection. In effect, higher seas make the same level of storm and even the same high tides more damaging than they used to be.

In Charleston, South Carolina, a six-lane highway floods when high tides prevent storm water from draining into the Atlantic, making it difficult for half the town’s 120,000 residents to get to three hospitals and police headquarters.

In Annapolis, Maryland, home to the U.S. Naval Academy, half a foot of water flooded the colonial district, a National Historic Landmark, at high tide on Chesapeake Bay during rainstorms on April 30, May 1, May 16 and Aug. 12.

Saxis Island resident and duck decoy carver Grayson Chesser takes to the water off this historic fis …

Engineers say there are three possible responses to rising waters: undertake coastal defense projects; adapt with actions like raising roads; or abandon land to the sea. Lacking a national strategy, the United States applies these measures haphazardly.

Congress actually recognized global warming way back in 1978 with passage of the National Climate Program Act. The law aimed to “assist the Nation and the world to understand and respond to natural and man-induced climate processes and their implications.”

But after $47 billion in direct federal spending on climate change research, Congress hasn’t passed a major piece of legislation to deal specifically with the effects of rising sea levels.

“In the U.S., you have best data set on what’s happening in the world, and yet it’s not used in public policy,” said Robert Nicholls, professor of coastal engineering at the University of Southampton in England and a contributor to the U.N.-sponsored Intergovernmental Panel on Climate Change.

The lack of clear policy is evident in Chincoteague, population 3,000.

NASA scientist William Krabill talks while on board a NASA P-3 plane at the NASA Wallops flight faci …

Most visitors come for the mile of ocean-facing public recreational beach, according to the U.S. Fish and Wildlife Service, which manages the refuge. Visitors can drive with all of their gear right up to the edge of the beach to park in a 1,000-space crushed-shell lot.

As erosion worsened, the cost to American taxpayers of repeated destruction of the parking lot and causeway from rising sea levels would only increase, Fish and Wildlife officials said. In 2010, the agency proposed moving the beach to a less-endangered site.

Town leaders pointed to a survey in which 80 percent of visitors said they would not continue coming to the beach if they had to park in town and take a shuttle. Residents also feared that Fish and Wildlife would let the southern end of Assateague Island erode away if the beach were moved.

A series of angry meetings with local Fish and Wildlife officials resolved nothing.

In 2012, Chincoteague got a hearing at the U.S. Capitol on the proposal. Wanda Thornton, an Accomack county supervisor, testified that local residents feared for their jobs.

The agency released a draft plan in May that would relocate the beach to the less unstable site, but keep the parking area at its current size, as long as there’s enough land to do so. As many residents feared, this plan would not replenish the sand at the southern end of Assateague or at the new site as they erode.

A public hearing in Chincoteague on June 26 failed to settle the matter.

(This is an abridged version of a special report. The full package, including unabridged text, interactive graphics and video, is on Reuters.com at http://reut.rs/1nyd8pK )

That means thinking about earthquakes, floods, tsunamis, solar storms, multiple failures and situations that seem freakishly unusual, according to Thursday’s National Academy of Sciences report. Those kinds of things triggered the world’s three major nuclear accidents.

“We need to do a soul searching when it comes to the assumptions” of how to deal with worst case events, said University of Southern California engineering professor Najmedin Meshkati, the panel’s technical adviser. Engineers should “think about something that could happen once every, perhaps 1,000 years” but that’s not really part of their training or nature, he said.

“You have to totally change your mode of thinking because complacency and hubris is the worst enemy to nuclear safety,” Meshkati said in an interview.

The report said the 2011 Japanese accident, caused by an earthquake and tsunami, should not have been a surprise. The report says another Japanese nuclear power plant also hit by the tsunami was closer to the quake’s fault. But the Onagawa plant wasn’t damaged because quakes and flooding were considered when it was built.

Onagawa had crucial backup electricity available for when the main power went down, as opposed to Fukushima which had emergency generators in a basement that flooded. Onagawa’s operators had “a different mindset” than the executives who ran Fukushima, Meshkati said.

FILE – This March 24, 2011, file photo shows a young evacuee being screened at a shelter for leaked …

The other two nuclear accidents — at Pennsylvania’s Three Mile Island and Ukraine’s Chernobyl— were caused by multiple system failures.

Lee Clarke, a Rutgers University risk expert and author of the book “Worst Cases,” criticized the academy’s report as too weak. He said the tone of the report made it seem like the accident was unpredictable and caught reasonable people by surprise “and it shouldn’t have.” But the report itself said the “the Fukushima accident was not a technical surprise.”

David Lochbaum of the activist group Union of Concerned Scientists said the problem is that federal law financially protects the U.S. nuclear industry from accidents gives utilities little incentive to spend money on low-probability, high-consequence problems.

But Nuclear Energy Institute senior vice president Anthony Pietrangelo said the American nuclear industry has already taken several steps to shore up backup power and deal with natural disasters.

“We cannot let such an accident happen here,” he said in a statement.

Another issue the report raised was about how far radiation may go in a worst case accident.

The U.S. Nuclear Regulatory Commission orders plants to have emergency plans for a zone of 10 miles around a nuclear plant. But the academy study said Fukushima showed that “may prove inadequate” if a similar accident happened in the U.S. People nearly 19 miles away in Japan needed protection from radiation. But the committee would not say what would be a good emergency zone.

The leaks identified by this study do not represent a safety threat but do add up to a large volume of smog-inducing, greenhouse gas emissions, EDF chief scientist Steven Hamburg told reporters during a media briefing about the pilot program Wednesday.

While utilities are federally mandated to address large gas leaks that pose hazards to property and people, smaller, chronic leaks typically fall by the wayside until the pipes can be fully replaced, Mr. Hamburg said.

“This work creates an important tool for helping to understand where the largest of these leaks are and where the dollars that are being spent to modernize and upgrade gas systems can best be utilized,” Hamburg said.

National Grid, a utility company that operates pipelines in Boston and Staten Island, plans to use the data gathered through this pilot program to prioritize replacement of aging pipelines, Susan Fleck, National Grid’s Vice President of Pipeline Safety, told reporters during the briefing.

The problem appears to be particularly pervasive in cities with aging infrastructure. In Boston and Staten Island – both of which rely on many pipes that are more than 50 years old – the sensors detected an average of one leak per every mile driven. Many cities in the Northeast rely on similarly aging infrastructures. By contrast, Indianapolis – which has invested heavily in updated natural gas pipes – yielded an average of just one leak per 200 miles driven.

For its part, Massachusetts adopted a uniform classification system for prioritizing repairs of leaks in natural gas pipelines in a new law signed by Gov. Deval Patrick (D) on July 7. The EDF report highlights this law as a point of progress in developing a process to plan and fund long-term pipeline upgrades.

Methane is a potent greenhouse gas that can have a short-term impact on climate up to 120 times greater than carbon dioxide, says Louis Derry, a professor of earth and atmospheric sciences at Cornell University in Ithaca, N.Y. Over the long term, however, methane is not a major factor in altering climate because it persists in the atmosphere for only 10 to 20 years, he says.

“Even if methane is not a major climate player, curbing emissions is the right thing to do because it will reduce the danger of small leaks growing into larger, more dangerous leaks and will help to improve overall air quality,” Professor Derry says. (Methane is a contributing factor in the formation of ozone and smog.)

The release of these findings in a user-friendly format could help to secure public buy-in for costly infrastructure improvements, Derry suggests.

Replacing pipelines “is expensive, nobody wants to pay for it, and nobody wants to have their street dug up,” he explains. The visualizations offered by the EDF maps could persuade the public to put up with rate increases and the nuisance of lengthy construction projects to overhaul corroding pipelines.

The most encouraging aspect of this study, Derry says, is its role as an illustration of the technological leap in sensing capabilities. Until just a few years ago, these measurements would have been collected by hand and individually processed in the laboratory, he says. Today, for about $50,000, researchers can affix a sensor capable of taking a reading every second to the roof of a car or the wing of an airplane.

“This is a highly, cost-effective way to cover large areas that just wasn’t possible a few years ago,” he says. That capability could be used to follow up in an area where pipes have been replaced to see whether the replacement was effective in curbing emissions. It could also be employed to measure other emissions such as water vapor or carbon dioxide.